Sync'ing FSX with FSFS:
Record r1517479,1518202,1526057,1526058,1527079,1527084,1527217,1527785,
1535029,1540417,1547045,1547079,1547096,1547450,1547866,1548097,1549947,
1555286,1561421,1563985,1568953,1568955,1573344,1588901,1595097 as being
already merged from /subversion/libsvn_fs_fs into subversion/libsvn_fs_x.

These changes have either already been duplicated manually, touched both
backends simultaneously or address FSFS legacy format support.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1595349 13f79535-47bb-0310-9956-ffa450edef68